The relationship between word length and threshold character size in patients with central scotoma and eccentric fixation

Background: Understanding limitations on text reading with eccentric fixation is of major concern in low vision research. Our objective was to determine, in patients with a central scotoma, whether threshold character size is similar for different word lengths and paragraphed texts. Methods: In 19 patients, we retrospectively analyzed the relationship between minimum readable character size for isolated words and text. Isolated letters, two, five, and ten-letter words and a paragraphed text were presented randomly through a scanning laser ophthalmoscope in eight different character sizes. Results: Threshold character size varied according to the text stimulus (p0.99), as were those for five-letter words, ten-letter words, and paragraphed text (p>0.99). Threshold character size for single letters and two-letter words was significantly lower than that measured with other text stimuli. Discussion: Reading performance is influenced by a variety of factors such as crowding, contextual effects, visual span, degree of oculomotor adaptation needed, and frequency of a defined word. Globally, when reading with a central scotoma, it appears that within word characteristics have more impact than inter-word parameters on threshold character siz

Peripheral myopization using a dominant design multifocal contact lens

Purpose: The purpose of this study was to characterize the central and peripheral refraction across the horizontal meridian of the visual fi eld without and with a multifocal dominant design soft contact lens of different add powers (+1.00 D to +4.00 D) in emmetropic eyes. Methods: Twenty right eyes from 20 emmetropic patients (mean spherical equivalent central refraction —0.06 ± 0.54 D) with a mean age of 21.6 ± 2.3 years were fi tted with Proclear Multifocal dominant design (Coopervision, Pleasanton, CA, USA). Lenses had add powers from +1.00 to +4.00 D in 1.00 D steps. The central and peripheral refraction was measured along the horizontal meridian up to 35º of eccentricity in the nasal and temporal retinal area in 5º steps using a open-fi eld autorefractometer. Results: Only the +3.00 and +4.00 D add powers generated a signifi cant change in the peripheral refractive pattern compared to central refraction and compared with the no-lens wearing situation. The average myopic increase with these lenses was —3.00 D and —5.00 (p < 0.001) at the margins of inspected nasal and temporal visual fi eld, respectively. Conclusions: Multifocal dominant design soft contact lenses are able to change the peripheral refractive profi le in emmetropic eyes increasing relative peripheral myopia. Lenses with +3.00 D add power seem to be the best option to create such effect due to signifi cant peripheral myopization.Objetivo: El objetivo de este estudio fue caracterizar la refracción central y periférica a través del meridiano horizontal del campo visual con y sin lente de contacto blanda multifocal de diseño dominante de diferentes adiciones (+1,00 D a +4,00 D) en ojos emétropes. Métodos: Se colocaron lentes multifocales de diseño dominante Proclear (Coopervision, Pleasanton, Estados Unidos) en 20 ojos derechos de 20 pacientes emétropes (media del equivalente esférico de refracción central, —0,06 ± 0,54 D) con una media de edad de 21,6 ± 2,3 años. Las lentes tenían adiciones desde +1,00 hasta +4,00 D en pasos de 1,00 D. Se evaluó la refracción periférica a través del meridiano horizontal hasta 35º de excentricidad en el campo retiniano nasal y temporal en pasos de 5º utilizando un autorrefractómetro de campo abierto. Resultados: Solamente las potencias de +3,00 y +4,00 D produjeron un cambio signifi cativo en el patrón de refracción periférica en comparación con la refracción central y en comparación con la evaluación sin lente. El aumento medio de la miopía con estas lentes fue de —3,00 D y —5,00 (p < 0,001) en los límites de los campos visuales nasal y temporal explorados, respectivamente. Conclusiones: Las lentes de contacto blandas, multifocales y de diseño dominante tienen la capacidad de cambiar el perfi l de refracción periférica en ojos emétropes incrementando la miopía relativa periférica. Aparentemente, las lentes con potencia de +3,00 D serían la mejor opción para generar ese efecto debido a la miopización periférica significativaMRIS -Ministry of Research, Innovation and Science(SAF2008-01114-E

The Effect of Fractal Contact Lenses on Peripheral Refraction in Myopic Model Eyes

Purpose: To test multizone contact lenses in model eyes: Fractal Contact Lenses (FCLs), designed to induce myopic peripheral refractive error (PRE). Methods: Zemax ray-tracing software was employed to simulate myopic and accommodation-dependent model eyes fitted with FCLs. PRE, defined in terms of mean sphere M and 90–180 astigmatism J180, was computed at different peripheral positions, ranging from 0 to 35 in steps of 5, and for different pupil diameters (PDs). Simulated visual performance and changes in the PRE were also analyzed for contact lens decentration and model eye accommodation. For comparison purposes, the same simulations were performed with another commercially available contact lens designed for the same intended use: the Dual Focus (DF). Results: PRE was greater with FCL than with DF when both designs were tested for a 3.5 mm PD, and with and without decentration of the lenses. However, PRE depended on PD with both multizone lenses, with a remarkable reduction of the myopic relative effect for a PD of 5.5 mm. The myopic PRE with contact lenses decreased as the myopic refractive error increased, but this could be compensated by increasing the power of treatment zones. A peripheral myopic shift was also induced by the FCLs in the accommodated model eye. In regard to visual performance, a myopia under-correction with reference to the circle of least confusion was obtained in all cases for a 5.5 mm PD. The ghost images, generated by treatment zones of FCL, were dimmer than the ones produced with DF lens of the same power. Conclusions: FCLs produce a peripheral myopic defocus without compromising central vision in photopic conditions. FCLs have several design parameters that can be varied to obtain optimum results: lens diameter, number of zones, addition and asphericity; resulting in a very promising customized lens for the treatment of myopia progression.This research was supported by the Ministerio de Economia y Competitividad (grant FIS2011-23175), the Generalitat Valenciana (grant PROMETEO2009-077) and the Universitat Politecnica de Valencia (grant INNOVA SP20120569), Spain.Rodríguez Vallejo, M.; Benlloch Fornés, JI.; Pons Martí, A.; Monsoriu Serra, JA.; Furlan, WD. (2014). The Effect of Fractal Contact Lenses on Peripheral Refraction in Myopic Model Eyes. Current Eye Research. 39(12):1-10. https://doi.org/10.3109/02713683.2014.903498S110391

A technique to train new oculomotor behavior in patients with central macular scotomas during reading related tasks using scanning laser ophthalmoscopy: immediate functional benefits and gains retention

BACKGROUND: Reading with a central scotoma involves the use of preferred retinal loci (PRLs) that enable both letter resolution and global viewing of word. Spontaneously developed PRLs however often privilege spatial resolution and, as a result, visual span is commonly limited by the position of the scotoma. In this study we designed and performed the pilot trial of a training procedure aimed at modifying oculomotor behavior in subjects with central field loss. We use an additional fixation point which, when combined with the initial PRL, allows the fulfillment of both letter resolution and global viewing of words. METHODS: The training procedure comprises ten training sessions conducted with the scanning laser ophthalmoscope (SLO). Subjects have to read single letters and isolated words varying in length, by combining the use of their initial PRL with the one of an examiner's selected trained retinal locus (TRL). We enrolled five subjects to test for the feasibility of the training technique. They showed stable maculopathy and persisting major reading difficulties despite previous orthoptic rehabilitation. We evaluated ETDRS visual acuity, threshold character size for single letters and isolated words, accuracy for paragraphed text reading and reading strategies before, immediately after SLO training, and three months later. RESULTS: Training the use of multiple PRLs in patients with central field loss is feasible and contributes to adapt oculomotor strategies during reading related tasks. Immediately after SLO training subjects used in combination with their initial PRL the examiner's selected TRL and other newly self-selected PRLs. Training gains were also reflected in ETDRS acuity, threshold character size for words of different lengths and in paragraphed text reading. Interestingly, subjects benefited variously from the training procedure and gains were retained differently as a function of word length. CONCLUSION: We designed a new procedure for training patients with central field loss using scanning laser ophthalmoscopy. Our initial results on the acquisition of newly self-selected PRLs and the development of new oculomotor behaviors suggest that the procedure aiming primarily at developing an examiner's selected TRL might have initiated a more global functional adaptation process

Results of pipe bend analysis, Part VII - stress distributions in flanged pipe elbows from an out-of-plane force.

Graphs of outside surface stress distributions are presented and numerical values of stresses on inside and outside surfaces tabulated for a wide range of flange-ended pipe elbows subjected to an out-of-plane force applied to one flange; calculations are based on linear thin shell theory

Results of pipe bend analysis, Part VIII - stresses in elbows with long tangents under in-plane bending.

Graphs of outside surface stress distributions are presented and numerical values of stresses on inside and outside surfaces tabulated for wide range of 90O pipe bends with long tangent pipes subjected to in-plane bending; calculations based on linear thin shell theory

Results of pipe bend analysis, Part VI - stress distributions in flanged pipe elbows from out-of-plane bending.

Graphs of outside surface stress distributions are presented and numerical values of stresses on inside and outside surfaces tabulated for a wide range of flange-ended pipe elbows subjected to a pure out-of-plane bending moment applied at one flange and pure torsion at the other; calculations are based on linear thin shell theory

Results of pipe bend analysis, Part IX - stress distributions in flanged pipe elbows from in-plane shear.

Graphs of outside surface stress distributions are presented and numerical values of stresses on inside and outside surfaces tabulated for a wide range of flange-ended pipe elbows subjected to an in-plane shear force applied to one flange; calculations based on linear thin shell theory

Results of pipe bend analysis, Part 4 - flexibility factors of pipe bends with flanged tangents.

An equivalent flexibility factor is defined for pipe bends with flanged tangent pipes under pure in-plane bending, and numerical values of this factor are presented for a range of 90o and 180o bends with various tangent lengths

Results of pipe bend analysis, Part 2 - stress distributions from bending flanged pipe elbows.

Graphs of outside surface stress distributions are presented and numerical values of stresses on inside and outside surfaces tabulated for a wide range of flange-ended pipe elbows subjected to pure in-plane bending. Calculations are based on linear thin shell theory